This invention relates to bonding, and, more particularly, to a rotary bonding apparatus in which the bonding elements are mounted on a rotating drum. The bonding elements remain stationary relative to web material which is supported on the drum during bonding.
Ultrasonic bonding and thermo bonding are commonly used for bonding various types of web material. For example, disposable diapers conventionally include moisture absorbent material which is sandwiched between outer layers of moisture impervious material such as polyethylene. The edges of the moisture impervious layers are bonded to seal the interior of the diaper.
Ultrasonic bonding is also conventionally used for making other types of garments, bags, and a wide variety of other products.
The principles of ultrasonic bonding and thermo bonding and the bonding equipment are well known and need not be described herein. Ultrasonic bonding is conventionally performed with an ultrasonic horn and an anvil. The material to be bonded is positioned between the horn and the anvil. High frequency electrical energy is converted to mechanical vibrations which are applied by the horn to the material.
Process variables for ultrasonic bonding include amplitude, pressure, and time. During the bonding time the material to be bonded is pressed between the horn and the anvil.
When products are formed from web material, for example, diapers, bags, etc., the web material may be advanced from an unwind to the horn and anvil. During the bonding time, the web material should be substantially stationary relative to the horn and the anvil.
Some ultrasonic bonding devices include horns and anvils which allow some limited movement with the web so that bonding can be performed without stopping the web. However, the bonding times that can be obtained without stopping the web are relatively short.
One or more bonding assemblies are mounted on a rotating drum. Web material is advanced to the drum and is supported by the drum as the drum rotates. Since the bonding assembly rotates with the drum, the bonding assembly is stationary relative to the drum. Bonding can be performed throughout the time during which the web material is supported by the drum without stopping the web. The bonding assembly can be an ultrasonic horn and anvil for ultrasonic bonding or a pair of heated elements for thermo bonding.